1. Field of the Invention
The invention generally relates to a light guide bar and an optical touch panel utilizing the light guide bar; particularly, the present invention relates to a light guide bar that has a plurality of prisms for changing the angle of an exiting light to increase brightness and uniformity so as to improve the touch-sensing effect of the optical touch panel utilizing the light guide bar.
2. Description of the Prior Art
Due to the characteristics of easy-to-operate, the touch display panel is widely used as the operating interface of computer information system including booking system and register system in many public places like railway stations, post offices, and hospitals. According to the sensing principle, the touch display panels may be classified into the following types: resistive, capacitive, and optical. The resistive or capacitive display panel, however, must use a plurality of resistors or capacitors, but the transmission rate of light is limited by the physical character of the device. Compared with the resistive or capacitive display panel, under the trend of large touch display panel, the optical touch display panel has natural superiority.
FIG. 1A is a schematic view of the known optical touch panel. As shown in FIG. 1A, the optical touch panel generally includes an infrared light-emitting diode 1, a light guide bar 2, a sensor 3 and other components. Infrared light is generated by the infrared light-emitting diode 1 and is guided to a sensing area 4 through the light guide bar 2, and the sensor 3 senses the infrared light over the sensing area 4. The sensor 3 will sense the variation of infrared energy over the sensing area 4 and will further determine the touch coordinates when a user touches the sensing area 4. The sensing of the sensor 3 is influenced by the infrared light over the sensing area 4. In order to improve the sensing result, microstructures are formed on a structure surface 6 opposite to a light-exiting surface 5 of the infrared light.
General microstructure is formed by methods like the printing. However, the microstructure formed by the methods like the printing only improves the brightness of the infrared light emitted from the light guide bar 2, and the microstructure contributes less to the uniformity. FIG. 1B is a schematic view of the brightness performance of the known optical touch panel. As shown in FIG. 1B, the general microstructure applies the distribution of infrared energy (or the brightness) to concentrate on the viewing angle between −70° and −80° (the viewing angle herein is from the normal of the light-exiting surface 5), and this non-uniform energy distribution will cause the sensor 3 to sense erroneously or lose efficacy.